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What is a microburst?

Posted on 5 July 2010

What is a microburst?

A microburst, illustrated (NASA)

A microburst is a small column of fast-sinking air, below a thunderstorm that reaches the ground and causes strong winds. A microburst, aka downdraft, is typically less than 2.5 miles wide, but it can produce winds of more than 100 mph and cause significant damage. It is also sometimes called a “downburst” or a “macroburst” if its path of destruction exceeds about 2.5 miles.

Microbursts last only 5 to 15 minutes. They develop when rain falling from a thunderstorm evaporates underneath the cloud, cooling the air beneath it. This cold, heavy air plunges to the surface and “splashes” against the ground like a bucket of cold water. The air then rushes sideways and its advancing edge swirls upward. Although he did not pursue it as a research topic, it is apparent from Leonardo DaVinci’s notes that he had considerable insight into microbursts!

Wind from a microburst can cause as much damage as a small tornado, flattening trees and power lines. Microbursts that occur near airports are particularly dangerous. Strong winds from above, below, and sideways buffet aircraft in just a few seconds. Planes that are landing or taking off are pushed into the ground, causing deadly crashes.

Microbursts have led to air disasters in New York City, Charlotte, New Orleans, and Dallas. Spurred by disasters, the U.S. government has spent millions of dollars on microburst detection equipment at airports. Fewer microburst-related disasters occur today, thanks to this technology and to extensive pilot training.

Steven A. Ackerman and Jonathan Martin are professors in the Department of Atmospheric and Oceanic Sciences at UW-Madison, are guests on the Larry Meiller‘s WHA-AM radio show the last Monday of each month at 11:45 a.m.